There is a bug on file for this (1495192), but if you are in a hurry to remove the DNT header now because you are worried about fingerprinting, you can use this extension.

Note on Private Windows

Extensions require specific permission to run in private windows. See: https://support.mozilla.org/kb/extensions-private-browsing.

Install

• License: Mozilla Public License 2.0
• Weekly downloads: 1
• Average daily users: 20
• Rating: 5/5 of 1 ratings
• Created: 2021-02-20 22:32:32
• Last updated: 2021-02-21 22:35:13
• Homepage: https://github.com/jscher2000/Remove-DNT-Do-Not-Track-Header
• Support site and email
• Orig: https://addons.mozilla.org/en-US/firefox/addon/remove-dnt-donottrack-header/
• API: remove-dnt@jeffersonscher.com